Liquid indection needle and liquid injection device

ABSTRACT

A liquid injection needle ( 10 ) includes a hollow needle part ( 2 ) for injecting a liquid ( 8 ) and a supporting part ( 3 ), to which the needle part ( 2 ) is fixed. The needle part ( 2 ) includes an anchoring part ( 22 ) that extends through the inside of the supporting part ( 3 ) and a puncturing part ( 21 ) that extends from the supporting part ( 3 ) for making a puncture in a living body. The puncturing part ( 21 ) has a distal side outer diameter equal to or greater than 0.1 mm and equal to or less than 0.25 mm, and a proximal side outer diameter than the distal side outer diameter.

TECHNICAL FIELD

[0001] The present invention generally pertains to a liquid injectionneedle and a liquid injection device. More particularly, the inventionrelates to a liquid injection needle and a liquid injection device usedfor percutaneously injecting drug solutions for living bodies intoliving bodies intracutaneously, subcutaneously, or intramuscularly.

BACKGROUND ART

[0002] An example of a known drug injection device used for injectingdrug solutions into living bodies is shown in FIG. 1. The drug injectiondevice 101 includes a needle 102 for injecting a drug solution, asupporting part 103 for supporting the needle 102, a substantiallycylindrical shaped main body 104 for containing the drug, and a plunger105 for injecting the drug contained inside the main body 104. Theneedle 102 consists of a hollow needle having a constant outer diameter,one end of which is firmly fixed to the supporting part 103, and iscapable of communicating with the inner space of the main body 104.

[0003] However, the needle 102 has an outer diameter larger than 0.3 mmand is relatively thick. As a result, pain may result to the patientwhen the needle 102 punctures the living body or injects a drug solutioninto the living body. Also, considering the size of the needle, thethought of being punctured with the needle can cause anxiety to thepatient.

[0004] Using a thinner needle to reduce the pain and/or anxiety to thepatient has its own problems. For example, it is extremely difficult tofix a thin needle to the supporting part in order to assemble a druginjection device. There is also a concern that a thin needle may beunable to puncture the skin of a living body and may end up bending dueto its lack of physical strength.

[0005] Moreover, a thin needle naturally has a small inner diameter, andso an excessively large force may be required to suck the drug solutionfrom a container such as a vial or inject the drug into the living body.Thus, a potential problem exists in that a thin needle may require alarge force for sucking the drug solution from a container or injectingthe drug into the living body.

[0006] Drug injection devices to be used for percutaneousself-administration of insulin solutions (the solutions containinginsulin) by diabetic patients are available on the market. The thinnestouter diameter available on such drug injection devices is 0.254 mm (31G (Gage)). The “Gage” is a number based on the B.W.G. (Birmingham WireGage) standard.

[0007] Unfortunately, the injection resistance felt in injecting drugsolutions using a 31 G needle is substantially large. This is due to thefact that the injection resistance increases theoretically in inverseproportion to the fourth power of the needle diameter.

[0008] Therefore, there is a concern that a patient with weak strengthsuch as a female, child, or aged person may have problem in injecting adrug solution in case of subcutaneous self-administration using a 31 Gneedle because the force usable for pressing the plunger of a druginjection device is poor. In such a case, the patient has no choice butto use a thicker needle, for example, a needle with an outer diameter of0.30 mm (30G), which causes less injection resistance, but greater pain.

[0009] Another problem in using a 31 G needle is that the insulinsolution may leak through the punctured hole in the skin or from the tipof the needle. One of the causes of such a problem is the following.

[0010] A needle as thin as a 31 G needle requires a long time tocomplete the injection of the drug solution as it has a high injectionresistance. Consequently, the patient may become impatient and pull theneedle out of the skin before the entire administration amount of thedrug to be delivered per injection (i.e., insulin unit) is administeredsubcutaneously.

[0011] The insulin unit is predetermined for each diabetic patient andit is essential to administer an exact amount per each injection.Leakage of the drug solution after injection means that an amount lessthan the required amount is administered, hence being unable to providesufficient curing effect.

[0012] In the field of dental treatments, drug injection devices areused for injecting anesthetic drugs, such as lidocaine, into thepatient's dental pulp. The thinnest needle available on the market fordrug injection devices for dental use has an outer diameter of 0.26 mm.

[0013] A substantially high injection resistance develops when a dentalneedle with an outer diameter of 0.26 mm is used for injectinganesthetic drugs into dental pulps and the like. Therefore, the mainbody of the device and the plunger are made of metals requiring a doctorwith a normal, healthy body for injecting an anesthetic drug. Thus, itis possible to inject an anesthetic drug even with such a thin needle,if a very large force is applied to the plunger.

[0014] However, because the device and the plunger are made of metal,the device is relatively heavy and difficult to handle. If injectionresistance can be reduced, lighter materials such as plastics can beused to form the device and injection can be done with less force.Hence, it is possible to provide a lighter and easier to use druginjection device for dental use.

[0015] Moreover, as mentioned above, a thicker needle is not preferableas it tends to create anxiety in the patient, although it can reduceinjection resistance. In other words, it is preferable to use a thinnerneedle to reduce or alleviate pain or anxiety to the patient in a dentaldrug injection device as well.

[0016] Thus, although very thin needles can reduce or alleviate pain tothe patient, problems exist such as difficulty of manufacture, lack ofstrength and high injection resistance. Such needles are thus notpractically used.

[0017] An object of the present invention is to provide a very thinliquid injection needle, and a liquid injection device equipped withsuch liquid injection needle, that are capable of alleviating pain tothe patient, being relatively easy to manufacture, providing sufficientstrength, and causing less injection resistance.

DISCLOSURE OF INVENTION

[0018] A liquid injection needle of the invention includes a hollowneedle part for injecting a liquid and a supporting part to which theneedle part is fixed, wherein the needle part comprises an anchoringpart that extends through the inside of the supporting part and apuncturing part that extends from the supporting part for making apuncture in a living body. The puncturing part has a distal side outerdiameter equal to or greater than 0.1 mm and equal to or less than 0.25mm, and a proximal side outer diameter greater than the distal sideouter diameter.

[0019] According to another aspect, a liquid injection needle includes ahollow needle part for injecting a liquid and a supporting part to whichthe needle part is fixed, wherein the needle part has an anchoring partthat extends through the inside of the supporting part and a puncturingpart that extends from the supporting part for making a puncture in aliving body. The puncturing part has a proximal side outer diametergreater than a distal side outer diameter and possesses a stickingresistance equal to or less than 7 gram-force.

[0020] In accordance with another aspect, a liquid injection needleincludes a hollow needle part for injecting a liquid and a supportingpart to which the needle part is fixed, wherein the needle part has ananchoring part that extends through the inside of the supporting partand a puncturing part that extends from the supporting part for making apuncture in a living body. The puncturing part has a proximal side outerdiameter greater than a distal side outer diameter, and the needle parthas a flow path resistance equal to or less than 350 gram-force under asustained water flow rate of 20 μl/sec.

[0021] Another aspect involves a liquid injection device provided withthe above-described liquid injection needle, wherein the liquidinjection device includes a main body having an internal space adaptedto contain the liquid, with the supporting part being provided on oneend part of the main body. The needle part of the liquid injectionneedle is fixed on the supporting part to communicate with the internalspace.

BRIEF DESCRIPTION OF DRAWINGS

[0022] The foregoing and additional features and characteristics of thepresent invention will become more apparent from the following detaileddescription considered with reference to the accompanying drawingfigures in which like reference numerals designate like elements.

[0023]FIG. 1 is a side view of a known drug injection device.

[0024]FIG. 2 is a side view of a drug injection device of an embodimentaccording to the present invention.

[0025]FIG. 3 is a cross-sectional view of the drug injection deviceshown in FIG. 2.

[0026]FIG. 4 is a side view of a drug injection needle of the druginjection device shown in FIG. 2.

[0027]FIG. 5 is a cross-sectional view of the drug injection needleshown in FIG. 4.

[0028]FIG. 6 is an expanded cross-sectional view of a drug injectionneedle according to example 1 used for sticking resistance measurement.

[0029]FIG. 7A is a side view of a drug injection needle illustrating afirst grinding angle of the drug injection needle.

[0030]FIG. 7B is a view of a drug injection needle illustrating a secondgrinding angle of the drug injection needle.

[0031]FIG. 7C is a cross-sectional view taken along the section line A-Ain FIG. 7A illustrating a cross-sectional angle of the drug injectionneedle.

[0032]FIG. 8 is a graph showing sticking resistance measurement resultsof example 1.

[0033]FIG. 9 is a schematic illustration of a flow path resistancemeasurement system.

[0034]FIG. 10 is a cross-sectional view of explaining a method forconnecting a needle mounting part and a needle part according to theflow path resistance measurement system.

[0035]FIG. 11 is a graph showing the results of the flow path resistancemeasurement of example 1.

[0036]FIG. 12 is a table showing the results of the sticking and flowpath resistance measurement of examples 2-12.

[0037]FIG. 13 is a cross-sectional view of a drug injection deviceaccording to another embodiment.

[0038]FIG. 14 is a cross-sectional view of a drug injection deviceaccording to another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0039] Referring initially to FIGS. 2 and 3, a drug injection device 1according to one embodiment includes a drug injection needle 10 and amain body 4. The drug injection needle 10 has a hollow needle part 2possessing a special shape and a supporting part 3 to which one end ofthe needle part 2 is firmly fixed. The main body 4 is substantiallycylindrical in shape and has an internal space 41 into which a plunger 5is inserted allowing the plunger 5 to reciprocate longitudinally.

[0040] In general, drug solution 8 is sucked from a container such as avial into the internal space 41 through the needle part 2, and isinjected into the living body from the tip of the needle part 2 bypushing the plunger 5 into the main body 4.

[0041] The supporting part 3 located on one end (i.e., the left end inFIGS. 2 and 3) of the main body 4 has a passage 31 formed to communicatewith the internal space 41 of the main body 4. The base of the needlepart 2 is fixed in a liquid-tight manner to the internal surface of thepassage 31. Therefore, the needle part 2 communicates with the internalspace 41 of the main body 4 via the passage 31.

[0042] In the illustrated embodiment, the supporting part 3 and the mainbody 4 are formed integrally. However, it is also possible to form thesupporting part 3 and the main body 4 separately, and fix the supportingpart 3 to the end of the main body 4 by way of gluing or welding. It isalso possible to detachably mount the supporting part 3 to the end ofthe main body 4 by way of threading or fitting.

[0043] On the other end (i.e., the right end in FIGS. 2 and 3) of themain body 4, an opening 42 is provided to insert the plunger 5 into theinternal space 41. A gasket 6 is provided on the tip of the plunger 5that fits closely into the inner wall of the main body 4. The gasket 6serves a sealing function so that the drug solution does not leakbackward when the plunger 5 moves toward the supporting part 3.

[0044] The drug solution 8 is, for example, a liquid solution, a gel ora suspension containing a drug. The device is applicable to any drug, aslong as it is not a drug unsuitable for percutaneous administration.

[0045] Major drugs that can be included in this category areantibacterial drugs, antiviral drugs, vaccines, antineoplastic drugs,immunosuppressive drugs, steroid, antiinflamatory drugs, antirheumaticdrugs, arthritis drugs, antihistamic drugs, antiallergic drugs,antidiabetic drugs, hormone agents such as growth hormone, bone calciummetabolic drugs, vitamins, blood products, hematopoietic drugs,antithrombotic drugs, hypolipidemic drugs, antiarrhythmic drugs,vasodilator drugs, prostaglandin, calcium antagonistic drugs, ACEinhibitors, β blockers, antihypertensive drugs, diuretic drugs, xanthinederivatives, β agonists, antasthmatic drugs, antitussive drugs,expectorants, anticholinergic drugs, antidiarrheal drugs, digestants,antiulcer drugs, cathartic drugs, hypnotic drugs, sedative drugs,antipyretic drugs, cold remedies, antiepileptic drugs, antipsychoticdrugs, antidepressive drugs, antianxiety drugs, central nerve irritantdrugs, parasympathetic drugs, sympathetic drugs, antiemetic drugs,central stimulants, antiparkinsonism drugs, muscle relaxants,anticonvulsants, anesthetic agents, antipruritic drugs, migraine drugs,oligonucleotides, gene drugs, etc.

[0046] Drugs that are ineffective or become less effective when orallyadministered, for example, peptide, protein, polysaccharide,oligonucleotide, DNA, etc., are more preferable for this application.

[0047] The injection amount of the drug solution 8 per eachadministration is set up equal to the single administration amount ofconventional injection drugs, which is 1 ml or less in most cases, orbetween 0.01 and 2 ml.

[0048] The gasket 6 is made of butyl rubber, silicone rubber, elastomer,etc., and is formed by a molding process. The supporting part 3, themain body 4; and the plunger 5 are made of plastic materials such aspolypropylene, and polyethylene, and formed by a molding process.

[0049] The main body 4, the supporting part 3, and the plunger 5 aremade partially or totally of a transparent material so that the user canvisually check the quantity of the drug solution 8 contained in theinternal space 41. The surface of the main body 4 has a scale 7 so thatthe user can check the amount of drug solution 8 contained or injected.

[0050] The needle part 2 has a puncturing part 21 and an anchoring part22 as shown in FIG. 4 and FIG. 5. The puncturing part 21 is an extensionpart protruding outward from the supporting part 3 and is adapted to bestuck into the living body. The anchoring part 22 is an extension partthat extends into the inside of the supporting part 3, and connects orcommunicates with the passage 31 that communicates with the internalspace 41 of the main body 4.

[0051] The tip of the puncturing part 21 has a slanted part 21 a forminga blade surface that can be stuck into the skin. The blade surface isformed by slicing the tip at an angle.

[0052] The distal side outer diameter of the puncturing part 21, i.e.,the outer diameter of the puncturing part 21 in the vicinity of theslanted part 21 a should be equal to or larger than 0.1 mm and equal toor smaller than 0.25 mm, preferably equal to or larger than 0.1 mm andequal to or smaller than 0.23 mm, more preferably equal to or largerthan 0.1 mm and equal to or smaller than 0.20 mm.

[0053] The upper limit of the distal side outer diameter of thepuncturing part 21 is set smaller than the conventional size from thestandpoint of reducing the sticking pain to the patient. The lower limitis set from the standpoint of securing the desired strength andsuppressing the increase of flow path resistance during the drugsolution injection. The distal side internal diameter of the puncturingpart 21 is preferably equal to or larger than 0.05 mm and equal to orsmaller than 0.15 mm, preferably equal to or larger than 0.05 mm andequal to or smaller than 0.13 mm, more preferably equal to or largerthan 0.05 mm and equal to or smaller than 0.10 mm.

[0054] In the process of percutaneous puncture by way of a needle,nociperception is induced generally as a result of the tip of the needleadvancing into the deeper area of the skin, tearing up the skin andcausing irritation and damage in the nerves and veins related to thepain.

[0055] However, the distal side outer diameter of the puncturing part 21is chosen extremely small in this embodiment. Therefore, irritation anddamage in the nerves and veins caused by the slanted part 21 a thatpunctures the skin and tears the living body are minimized. Thus, thepuncturing part 21 causes almost no puncturing pain to the patient.

[0056] On the other hand, the proximal side outer diameter of thepuncturing part 21 is chosen larger than the distal side outer diameterof the puncturing part 21. Therefore, strength sufficient for puncturingthe living body with the puncturing part 21 can be secured. This helpsprevent the user from causing an accidental breakage of the puncturingpart 21 and leaving the puncturing part 21 inside the living body.

[0057] Specifically, the proximal side outer diameter of the puncturingpart 21 is equal to or larger than 0.3 mm and equal to or smaller than 2mm, more preferably equal to or larger than 0.35 mm and equal to orsmaller than 1.5 mm, most preferably equal to or larger than 0.35 mm andequal to or smaller than 1 mm.

[0058] The lower limit of the proximal side outer diameter of thepuncturing part 21 is chosen larger than the distal side outer diameterof the puncturing part 21 from the standpoint of aggressively reducingthe flow path resistance during the drug solution injection as mentionedabove. Also, the upper limit of the proximal side outer diameter of thepuncturing part 21 is chosen to suppress the sticking resistance intothe living body. The proximal side internal diameter of the puncturingpart 21 should preferably be equal to or larger than 0.20 mm and equalto or smaller than 1.2 mm, preferably equal to or larger than 0.25 mmand equal to or smaller than 1.0 mm, more preferably equal to or largerthan 0.25 mm and equal to or smaller than 0.8 mm.

[0059] The total length L₀ of the puncturing part 21 is preferably equalto or larger than 1.5 mm and equal to or smaller than 15 mm, morepreferably equal to or larger than 3 mm and equal to or smaller than 10mm. The total length L₀ is defined as the length from the supportingpart 3 to the tip of the slanted part 21 a that punctures the skin.

[0060] The total length L₀ is normally 8 to 40 nm for conventionalsubcutaneous or intramuscular administrations. However, the upper limitof the total length L₀ of the puncturing part here is chosen shorterthan that from the standpoint of securing a desired strength andsuppressing an increase of flow path resistance during injection of adrug solution. The lower limit is chosen from the standpoint ofeffecting a more smooth puncturing into the living body.

[0061] The outer diameter of the puncturing part 21 is preferably equalto or larger than 0.1 mm and equal to or smaller than 0.25 mm for agiven length L₁ starting from the slanted part 21 a toward thesupporting part 3. The length L₁ should be set to {fraction (2/3)} ormore, or more preferably {fraction (4/5)} or more, of the total lengthL₀ if the total length L₀ is equal to or longer than 1.5 mm and equal toor shorter than 5 mm. If the total length L₀ is longer than 5 mm andequal to or shorter than 15 mm, the length L₁ should be set to 3/5 ormore, or more preferably equal to or larger than 3/5 and equal to orshorter than 4/5, of the total length L₀.

[0062] The lower limit of the length L₁ is chosen to minimize thesticking resistance by maintaining the outer diameter of the puncturingpart 21 small immediately after skin puncturing by the slanted part 21a. The upper limit of the length L₀ is chosen from the standpoint ofsecuring sufficient strength and suppressing the increase of the flowpath resistance as the time of drug solution injection.

[0063] The puncturing part 21 in this embodiment has a distal end 21 bthat contains the slanted part 21 a, a proximal end 21 d that has anouter diameter larger than that of the distal end 21 b, and a middlepart 21 c located between the distal end 21 b and the proximal end 21 d.

[0064] The outer diameter of the middle part 21 c changes continuously,and smoothly connects the distal end 21 b and the proximal end 21 d. Theinner diameter of the middle part 21 c reduces gradually toward thedistal end 21 b. Therefore, the drug solution 8 is accelerated as itpasses through the middle part 21 c to flow powerfully into the distalend 21 b.

[0065] The distal end 21 b and the proximal end 21 d can both be formedto have substantially constant outer diameters for the entire length asshown in the drawing figures or can be formed to have tapering shapes.

[0066] The outer diameter of the anchoring part 22 that extends throughthe inside of the supporting part 3 is similar to the outer diameter ofthe proximal end 21 d, and should be equal to or larger than 0.3 mm andequal to or smaller than 2 mm, preferably equal to or larger than 0.35mm and equal to or smaller than 1.5 mm, more preferably equal to orlarger than 0.35 mm and equal to or smaller than 1 mm.

[0067] The lower limit of the outer diameter of the anchoring part 22 ischosen to be larger than the distal side diameter of the puncturing part21 from the standpoint of aggressively reducing the flow path resistanceduring drug solution injection and increasing the area of junction withthe supporting part 3 to enhance the junction strength. The upper limitof the outer diameter of the anchoring part 22 is chosen from thestandpoint of suppressing the increase of the external dimension of thesupporting part 3. As a result, the inner diameter of the anchoring part22 should preferably be set equal to or larger than 0.20 mm and equal toor smaller than 1.2 mm, preferably equal to or larger than 0.25 mm andequal to or smaller than 1.0 mm, more preferably equal to or larger than0.25 mm and equal to or smaller than 0.8 mm.

[0068] The anchoring part 22 can be formed alternatively to have itsinner diameter increasing gradually toward the passage 31 of thesupporting part 3. Doing so will further reduce the flow path resistanceso that the drug solution 8 is accelerated as it passes through theanchoring part 22 to flow powerfully into the proximal end 21 d.

[0069] A suitable range of wall thickness of the needle part 2 varieswith the construction such as outer diameters and materials of thepuncturing part 21 and the anchoring part 22. Specifically, a distalside wall thickness of the puncturing part 21 is equal to or larger than20 μm and equal to or smaller than 50 μm, and a proximal side wallthickness of the puncturing part 21 and a wall thickness of theanchoring part 22 are equal to or larger than 50 μm and equal to orsmaller than 400 μm, preferably equal to or larger than 50 μm and equalto or smaller than 250 μm, more preferably equal to or larger than 50 μmand equal to or smaller than 130 a m.

[0070] The needle part 2 is made of stainless steel, for example, and isformed by a plastic working process. However, the needle part 2 canalternatively be made of other metals such as titanium, or othermaterials such as plastics.

[0071] The fixing of the needle part 2 to the supporting part 3 isaccomplished by an insert forming process or gluing. Since the needlegenerally has a small outer diameter, its junction to the supportingpart is relatively weak and may fall off from the supporting part. Tocounter this tendency, the outer diameter of the anchoring part 22 thatis fixed to the supporting part 3 is chosen to be larger than the distalside outer diameter of the puncturing part 21 in this embodiment.

[0072] In other words, the needle part 2 is firmly fixed to thesupporting part 3 via the anchoring part 22 having a large diameter toprevent the needle part 2 from falling off. Moreover, since the jointarea between the anchoring part 22 and the supporting part 3 is larger,it is easier to securely fix the needle part 2 to the supporting part 3.Therefore, it is easy to manufacture the drug injection needle 10 andthe drug injection device 1 despite the fact that the distal side outerdiameter of the puncturing part 21 is small.

[0073] Next, this embodiment will be described below from the standpointof the sticking resistance. The sticking resistance is defined by theload experienced in sticking a silicone rubber piece at a speed of 10mm/sec. The silicone rubber piece is 0.5 mm thick and its hardness,which is detected by a rubber hardness tester (durometer) based on K6253type A of the Japanese Industrial Standard, is A50 (referring to Section7619 of the International. Organization for Standardization).

[0074]FIG. 6 is an expanded cross-sectional view of the needle part 2according to example 1 used in the measurement of the stickingresistance. As shown in the drawing, the total length L₀ of thepuncturing part 21 is 8 mm or 13 mm, and the length L₀ of the distal end21 b is 2.75 mm.

[0075] The outer diameter and the inner diameter of the proximal end 21d are 0.35 mm and 0.25 mm respectively, and the outer diameter and theinner diameter of the distal end 21 b are 0.2 mm and 0.1 mm. The lengthof the middle part 21 c in which the outer diameter and the innerdiameter gradually reduce is 3.5 mm and the angle between contour lineand the axial line shown by the alternating long and short dash line is1 degree 50 minutes 28 seconds.

[0076] A first grinding angle α, a second grinding angle φ, and a crosssectional angle γ of the needle part 2 are 8.5, 18 and 129 degreesrespectively. As shown in FIG. 7A, the first grinding angle α is thebasic angle formed between the centerline of the distal end 21 b shownby the alternating long and short dash lines and the slanted part 21 a.In addition, as shown in FIG. 7B, the second grinding angle φ is theangle formed between the cut surface forming the blade surface of theslanted part 21 a and the centerline. Further, the cross sectional angleγ is, as shown in FIG. 7C, the angle formed between the edges of the twosides of the blade tip section (referring to Section 7864 of theInternational Organization for Standardization).

[0077] As a reference point, a needle available on the market intendedfor use on drug injection devices for percutaneous self-administrationof insulin solution by diabetes patients was used, with such needlehaving a constant outer diameter of 0.254 mm and a constant innerdiameter of 0.125 mm for the entire length, i.e., a 31 G needle wasused. The first grinding angle α, the second grinding angle φ, and thecross sectional angle γ of the 31 G needle were 9, 22 and 130 degreesrespectively.

[0078]FIG. 8 is a graph showing the measurement result of the stickingresistance of example 1, with the vertical axis and the horizontal axisshowing the load and the displacement respectively. As can be seen fromFIG. 8, the sticking resistance of the needle part 2 according to thepresent embodiment is markedly smaller than that of the conventional 31Gneedle in an area where a peak indicates a maximum load.

[0079] It can be seen from the graph that the maximum value of thesticking resistance of the conventional needle 31G is 8.4 gf(gram-force) (82.3 mN) and thus exceeds 8 gf (78.4 mN), while themaximum value of the sticking resistance of the needle part 2 is 6.4 gf(62.7 mN) and is thus less than 7 gf (68.6 mN). This evidences that theneedle part 2 according to the present embodiment has superiorcharacteristics with respect to the sticking resistance as compared tothe 31 G needle and is thus capable of reducing the sticking pain to thepatient.

[0080] Next, the present embodiment will be described below from thestandpoint of flow path resistance. The flow path resistance is definedas the driving force required for sustaining a constant flow of 20μl/sec using water. As shown in FIG. 9, the measuring system for theflow path resistance has a container 91 containing water 90, which isthe liquid used for the test, a pump 92 for transferring the suctionedwater 90 under a pressure, a recorder 93 for recording the dischargepressure of the pump 92 (i.e., the driving force), and a needle mountingpart 94 for detachably attaching the needle part, for which the stickingresistance is measured.

[0081] More specifically, the water 90 is pure water produced by areverse osmosis membrane, and the pump 92 is a metering pump usedgenerally for high-speed liquid chromatography. The needle mounting part94 and the needle part are detachably connected by way of a screw.

[0082] Specifically, as shown in FIG. 10, the needle part is connectedto a known needle hub 97 with an internally threaded part 96 by way ofadhesives or the like, and the internally threaded part 96 is screwed toan externally threaded part 95 formed on the needle mounting part 94.The externally threaded part 95 includes a hollow tube part 95 a, whichis inserted into the proximal end of the needle part to introduce thewater 90 into the needle part.

[0083] The recorder 93 records the discharge pressure of the pump 92 ata steady state when the flow quantity of the pump 92 is sustained at 20μl/sec.

[0084] The measurement of the flow path resistance was performed for thesame needle part 2 (example 1) according to the present embodiment usedin the sticking resistance measurement, and was also performed withrespect to two kinds of reference needles. One of the reference needlesis a 31 G needle that is the same as the needle used in the stickingresistance measurement as stated above, and the other is a 33 G needlehaving a constant outer diameter of 0.203 mm for the entire length,which corresponds to the outer diameter of the distal end 21 b of thepuncturing part 21, and a constant inner diameter of 0.105 mm for theentire length.

[0085]FIG. 11 is a graph showing the results of the flow pathmeasurement. As can be seen from the graph, the flow path resistance ofthe 31 G needle was about 272 gf (2.67 N), the flow path resistance ofthe 33 G needle was about 690 gf (6.76 N), and the flow path resistanceof the needle part 2 according to this embodiment was about 245 gf (2.40N).

[0086] Thus, the flow path resistance of the needle part 2 is less thana half of the flow path resistance of the 33 G (i.e., 350 gf (3.43 N))despite the fact that the outer diameter of the distal end 21 b of theneedle part 2 is equivalent to that of the 33 G needle.

[0087] More specifically, the 33 G needle exhibits a flow pathresistance of approximately 2.5 times the 31 G needle, and the needlepart 2 exhibits a flow path resistance of approximately 0.9 times the 31G needle. Thus, the needle part 2 according to the present embodimentpossesses better flow path resistance characteristics than the 31 G andthe 33 G needles.

[0088]FIG. 12 is a table showing the results of the sticking and flowpath resistance measurements for examples 2-12 having differentdimensions. As is apparent from these results, one of the needleexamples possesses a sticking resistance equal to 7.1 gf, another of theneedle examples possesses a sticking resistance of 7 gf, and all otherneedle examples possess a sticking resistance less than 7 gf. Inaddition, all of the needle examples possess a flow path resistance lessthan 350 gf. The needle examples thus all possess superiorcharacteristics.

[0089] Next, the method of using the drug injection device 1 will bedescribed. The drug solution 8 is sucked from a container such as a vialdirectly or via a rubber plug into the internal space 41 of the mainbody 4 of the drug injection device 1. Then, the puncturing part 21 ofthe needle part 2 is used to percutaneously make a puncture in the bodyof the patient, which is the target of the drug solution injection. Thedistal end 21 b of the puncturing part 21 is thinner than theconventional needle. Therefore, it is possible to reduce irritation ofthe nerves and blood vessels related to the pain and/or damage to thenerves and blood vessels, thus resulting in less pain generation.

[0090] By pressing the plunger 5, the drug solution 8 in the internalspace 41 is injected through the passage 31 of the supporting part 3,the anchoring part 22 and the puncturing part 21 of the needle part 2into various parts of the living body of the patient, e.g.,intracutaneous and subcutaneous parts, muscles, mucous membranes, orvarious internal organs.

[0091] The anchoring part 22 provides a sufficient junction forceagainst the supporting part 3 as its outer diameter is relatively large.Therefore, there is no possibility of the anchoring part 22 coming offfrom the supporting part 3. Moreover, the proximal end 21 d of thepuncturing part 21 provides sufficient strength as its outer diameter isrelatively large. Therefore, the puncturing part 21 is prevented frombreaking.

[0092] The inner diameters of the anchoring part 22 and the proximal end21 d of the puncturing part 21 are relatively large. Therefore, the flowpath resistances of the anchoring part 22 and the puncturing part 21 areminimized. Consequently, the force required to press the plunger 5 andpush out the drug solution 8 is smaller and the injection of the drugsolution 8 is performed smoothly and is thus improved.

[0093] It should be understood that this invention is not limited to theparticular embodiments shown and described above, but may be changed andmodified without departing from the technical concept of this invention.For instance, the shape of the distal end 21 b of the puncturing part 21does not necessarily have to have a constant outer diameter over itsentire length. For example, the distal end 21 b can have a taperingshape as shown in FIG. 13. The profile lines of the cross-section alongthe axis of the distal end 21 b can be straight or gradually curved.

[0094] As shown in FIG. 14, the outer diameter the puncturing part 21can be gradually reduced from the proximal end 21 d toward the slantedpart 21 a. The profile lines of the cross-section along the axis of thepuncturing part 21 can be straight or gradually curved.

[0095] Compared to the construction in which the outer diameter issubstantially constant for the entire length of the distal end 21 b, theembodiments shown in FIG. 13 and. FIG. 14 allow the outer diameter ofthe distal end 21 b in the vicinity of the slanted part 21 a to besmaller to thereby reduce the puncturing pain to the patient.

[0096] Moreover, because the internal diameter of the distal end 21 bgradually reduces toward the slanted part 21 a, the drug solution 8 isaccelerated when it passes through the distal end 21 b and thus flowsout of the slanted part 21 a more powerfully.

[0097] Although embodiments described above and illustrated in thedrawing figures depict the drug injection needle 10 as having only onepuncturing part 21, it is possible to arrange to have a plurality ofpuncturing parts 21 as well. With such an arrangement, it is possible toincrease the injection volume of the drug solution 8, so that a moreexpedient effect of the drug can be anticipated as the drug solution 8is distributed more efficiently into various parts of the living body.

INDUSTRIAL APPLICABILITY

[0098] As described in the above, the outer diameter of the distal endof the puncturing part can be made smaller in comparison with the knownprior art practices. For that reason, irritation and damage caused bythe puncturing part to blood veins and nerves, and related the pain, canbe reduced. Thus, pain to the patient can be decreased. The proximalside outer diameter of the puncturing part is larger than the distalside outer diameter, so that strength sufficient for making a puncturein the living body with the puncturing part can be secured or ensured.Therefore, it is possible to avoid situations in which it is notpossible to make a puncture due to breakdown of the puncturing part, forexample.

[0099] As the outer diameter of the anchoring part that extends throughthe supporting part has a larger diameter compared to the known design,the joint area between the anchoring part and the supporting part isincreased to allow the anchoring part to be fixed on the supporting partmore securely. Thus, the liquid injection needle and the liquidinjection device can be manufactured more easily despite the fact thatthe outer diameter of the distal end of the puncturing part isrelatively small.

[0100] Also, because the inner diameters of the proximal end of thepuncturing part and the anchoring part are made larger., the flow pathresistance during injection of the liquid into the living body can bereduced. This reduces the force required for injecting the liquid andmakes it possible to improve the injection of the fluid into the livingbody.

[0101] The principles, preferred embodiments and modes of operation ofthe present invention have been described in the foregoingspecification. However, the invention which is intended to be protectedis not to be construed as limited to the particular embodimentsdisclosed. Further, the embodiments described herein are to be regardedas illustrative rather than restrictive. Variations and changes may bemade by others, and equivalents employed, without departing from thespirit of the present invention. Accordingly, it is expressly intendedthat all such variations, changes and equivalents which fall within thespirit and scope of the present invention as defined in the claims, beembraced thereby.

1. A liquid injection needle comprising: a hollow needle part forinjecting a liquid; a supporting part to which the needle part is fixed;said needle part comprising an anchoring part that extends through aninside of said supporting part and a puncturing part that extends fromsaid supporting part for making a puncture in a living body; and saidpuncturing part having a distal side outer diameter equal to or greaterthan 0.1 mm and equal to or less than 0.25 mm, and a proximal side outerdiameter than said distal side outer diameter.
 2. The liquid injectionneedle as claimed in claim 1, wherein said proximal side outer diameteris equal to or greater than 0.3 mm and equal to or less than 2 mm. 3.The liquid injection needle as claimed in claim 1, wherein saidpuncturing part has a total length equal to or greater than 1.5 mm andequal to or less than 15 mm.
 4. The liquid injection needle as claimedin claim 1, wherein said puncturing part consists of a distal end, amiddle part and a proximal end, said distal end and said proximal endboth having constant outer diameters over their entire lengths, and saidmiddle part having an outer diameter that gradually reduces toward saiddistal end to smoothly connect said distal end and said proximal end. 5.The liquid injection needle as claimed in claim 1, wherein an outerdiameter of said puncturing part gradually decreases from saidsupporting part toward a tip of said puncturing part.
 6. The liquidinjection needle as claimed in claim 1, wherein said puncturing part hasa total length equal to or greater than 1.5 mm and equal to or less than5 mm, and said distal side outer diameter is equal to or greater than0.1 mm and equal to or less than 0.25 mm over a range that is {fraction(2/3)} or more of said total length.
 7. The liquid injection needle asclaimed in claim 1, wherein said puncturing part has a total lengthgreater than 5 mm and equal to or less than 15 mm, and said distal sideouter diameter is equal to or greater than 0.1 mm and equal to or lessthan 0.25 mm over a range that is {fraction (3/5)} or more of said totallength.
 8. The liquid injection needle as claimed in claim 1, whereinsaid liquid contains a drug that acts on a living body.
 9. The liquidinjection needle as claimed in claim 1, wherein said liquid isself-administered.
 10. The liquid injection needle as claimed in claim1, wherein the puncturing part possesses a sticking resistance equal toor less than 7 gram-force.
 11. The liquid injection needle as claimed inclaim 1, wherein said needle part possesses a flow path resistance equalto or less than 350 gram-force under a sustained water flow rate of 20μl/sec.
 12. A liquid injection needle comprising: a hollow needle partfor injecting a liquid; a supporting part to which the needle part isfixed; said needle part comprising an anchoring part that extendsthrough an inside of said supporting part and a puncturing part thatextends from said supporting part for making a puncture in a livingbody, said puncturing part having a proximal side outer diameter greaterthan a distal side outer diameter; and said puncturing part having asticking resistance equal to or less than 7 gram-force.
 13. The liquidinjection needle as claimed in claim 12, wherein said liquid contains adrug that acts on a living body.
 14. The liquid injection needle asclaimed in claim 12, wherein said liquid is self-administered.
 15. Theliquid injection needle as claimed in claim 12, wherein the needle partpossesses a flow path resistance equal to or less than 350 gram-forceunder a sustained water flow rate of 20 μl/sec.
 16. A liquid injectionneedle comprising: a hollow needle part for injecting a liquid; asupporting part to which the needle part is fixed; said needle partcomprising an anchoring part extending through an inside of saidsupporting part and a puncturing part extending from said supportingpart for making a puncture in a living body; said puncturing part havinga proximal side outer diameter greater than a distal side outerdiameter; and said needle part having flow path resistance equal to orless than 350 gram-force under a sustained water flow rate of 20 μl/sec.17. The liquid injection needle as claimed in claim 16, wherein saidliquid contains a drug that acts on a living body.
 18. The liquidinjection needle as claimed in claim 16, wherein said liquid isself-administered.
 19. A liquid injection device provided with saidliquid injection needle as claimed in claim 1, comprising a main bodyhaving an internal space adapted to contain said liquid, said supportingpart being provided at one end of the main body, said needle part ofsaid liquid injection needle being fixed on said supporting part tocommunicate with said internal space.
 20. The liquid injection device asclaimed in claim 19, wherein said proximal side outer diameter is equalto or greater than 0.3 mm and equal to or less than 2 mm.
 21. The liquidinjection device as claimed in claim 19, wherein said puncturing parthas a total length equal to or greater than 1.5 mm and equal to or lessthan 15 mm.
 22. The liquid injection device as claimed in claim 19,wherein said puncturing part includes a distal end, a middle part and aproximal end, said distal end and said proximal end both having constantouter diameters over their entire lengths respectively, and said middlepart having an outer diameter that gradually reduces toward said distalend to smoothly connect said distal end and said proximal end.
 23. Theliquid injection device as claimed in claim 19, wherein said puncturingpart has an outer diameter that gradually decreases from said supportingpart toward a tip of said puncturing part.
 24. The liquid injectiondevice as claimed in claim 19, wherein said puncturing part has a totallength equal to or greater than 1.5 mm and equal to or less than 5 mm,and said distal side outer diameter is equal to or greater than 0.1 mmand equal to or less than 0.25 mm over a range that is {fraction (2/3)}or more of said total length.
 25. The liquid injection device as claimedin claim 19, wherein said puncturing part has a total length greaterthan 5 mm and equal to or less than 15 mm, and said distal side outerdiameter is equal to or greater than 0.1 mm and equal to or less than0.25 mm over a range that is {fraction (3/5)} or more of said totallength.
 26. The liquid injection device as claimed in claim 19, whereinsaid liquid contains a drug that acts on a living body.
 27. The liquidinjection device as claimed in claim 19, wherein said liquid isself-administered.
 28. The liquid injection device as claimed in claim19, wherein said puncturing part possesses a sticking resistance equalto or less than 7 gram-force.
 29. The liquid injection device as claimedin claim 19, wherein said needle part possesses a flow path resistanceequal to or less than 350 gram-force under a sustained water flow rateof 20 μl/sec.
 30. A liquid injection device provided with said liquidinjection needle as claimed in claim 12, comprising a main body havingan internal space adapted to contain said liquid, said supporting partbeing provided at one end of the main body, said needle part of saidliquid injection needle being fixed on said supporting part tocommunicate with said internal space.
 31. The liquid injection device asclaimed in claim 30, wherein said liquid contains a drug that acts on aliving body.
 32. The liquid injection device as claimed in claim 30,wherein said liquid is self-administered.
 33. The liquid injectiondevice as claimed in claim 30, wherein said needle part possesses a flowpath resistance equal to or less than 350 gram-force under a sustainedwater flow rate of 20 μl/sec.
 34. A liquid injection device providedwith said liquid injection needle as claimed in claim 16, comprising amain body having an internal space adapted to contain said liquid, saidsupporting part being provided at one end of the main body, said needlepart of said liquid injection needle being fixed on said supporting partto communicate with said internal space.
 35. The liquid injection deviceas claimed in claim 34, wherein said liquid contains a drug that acts ona living body.
 36. The liquid injection device as claimed in claim 34,wherein said liquid is self-administered.